Prior to extracting fluids from a downhole formation, the fluids occupy space within the formation. In the process of producing fluids from a formation, the fluid pressure will generally decline. Reduced pore pressure in the reservoir rock will increase the effective stress and thereby cause the rock itself to shrink, and thus the reservoir will compact. Reservoir compaction may then cause subsidence at the surface. Subsidence is a substantial concern in the production of hydrocarbons, especially where the formation is comprised of unconsolidated sands or does not have significant structural integrity. Offshore platforms mounted to the seafloor and arranged to stand well above sea level and above any wave action at the sea surface have settled toward the sea because of subsidence. Actually, the amount of subsidence could be alarming if a substantial safety zone wasn't established in the design phase of the well development plan and such subsidence has been measured in as much as tens of feet.
The thickness of the producing zone typically diminishes to some extent during production of well fluids, but in poorly consolidated sands and high porosity rocks may diminish by a substantial amount such as about 10% over the life of the production operation. Compaction of the producing zones exerts powerful forces on equipment and pipe in the well. Conventional base pipe is subject to buckling when the compaction of the production string is less than 2 to 3% with relatively good lateral confinement supports and it is likely that the well will have to be abandoned or recompleted if the production string has buckled.